1. Field of the Invention
Embodiments of the invention generally relate to deposition of silicon-containing films, and more particularly to silicon compound compositions and related processes to deposit silicon-containing films.
2. Description of the Related Art
Atomic layer epitaxy (ALE) offers meticulous control of film thickness by growing single atomic layers upon a crystal lattice. ALE is employed to develop many group IV semiconductor materials, such as silicon, germanium, silicon germanium, silicon carbon and silicon germanium carbon. Silicon based materials, produced via ALE, are of interest for use as semiconductor materials. The silicon based materials can include germanium and/or carbon at selectable concentrations and are grown as polysilicon, amorphous or monocrystalline films. Silicon-ALE, in which a silicon-containing film is epitaxial grown, consists of two steps.
A monolayer of partially decomposed source gas molecules (e.g., SiH4 or SiH2Cl2) is adsorbed over the substrate or surface. The adsorbate may consists of a silicon atom and at least another kind of atom or group bonded with silicon, such as chlorine, hydrogen or methyl (e.g., SiCln, SiHn or H4-nSiMen, where n=1–4). The adsorbate decomposes to form adatoms of silicon on the surface. The adatoms migrate or diffuse on the surface to an empty lattice site of the silicon crystal. The crystal continues to form and grow as adatoms are generated on the crystalline surface and incorporated into the lattice. By-product removal is achieved and a new surface is created on the monolayer. The monolayer growth in the next cycle is made possible.
Source gases used during silicon deposition include lower silanes (e.g., silane, dichlorosilane and tetrachlorosilane) as well as higher silanes (e.g., disilane, hexachlorodisilane and trisilane). Silane and dichlorosilane are the most common source gases used during Si-ALE, such as described in U.S. Patent Publication Number. 20020052077. These lower silanes require the substrate to be maintained at high temperatures, often in the range of 800–1,000° C. Higher silanes are utilized as source gases to lower the temperature needed during Si-ALE. Disilane is used to grow silicon by ultraviolet-photostimulated ALE in the temperature range of 180–400° C., as demonstrated by Suda, et al., J. Vac. Sci. Technol. A, 8 (1990) 61., as well as by Lubben, et al., J. Vac. Sci. Technol. A, 9 (1991) 3003. Furthermore, trisilane is used as a source gas during Si-ALE at about 380° C., as reported by Imai, et al., Jpn. J. Appl. Phys., 30 (1991) 3646.
Si-ALE with supplemental etchants has also been realized. U.S. Patent Publication No. 20020127841 teaches the combination of dichlorosilane and hydrogen chloride to accomplish selective silicon growth. Supplemental etchants are generally halogenated and/or radical compounds (e.g., HCl or .Cl) that necessitate high reactivity. Therefore, hazardous and toxic conditions are often associated with etchant use.
Therefore, there is a need to provide silicon-containing compounds that provide both a source chemical for silicon deposition and a source chemical as an etchant. The silicon-containing compounds should be versatile to be applied in a variety of silicon deposition techniques.